This invention is directed to a crossed-field plasma mode electric conduction control device wherein the interelectrode space between a pair of electrodes is subjected to an interelectrode electric field and a magnetic field at right angles thereto. Gas and magnetic conditions are such as to permit interelectrode electric conduction by controlling low pressure glow mode plasma discharge.
Previous crossed-field tubes and other Penning discharge devices have conventionally been constructed with a high degree of symmetry. In a crossed-field switch device for high power off-switching, a uniform distribution of plasma is required in the device. Thus, they have been designed with a magnetic field throughout the entire active interelectrode zone which channels the ionizing electrons around in the ExB direction. When the magnetic field is reduced below a critical level, the energetic electrons are uniformally lost to the anode and plasma generation ceases throughout the interelectrode gap. This results in a bistable operating characteristic with a sharp on-off dependence on the magnetic field.
R. J. Harvey, U.S. Pat. No. 4,071,801 describes a crossed-field switch device having a single interelectrode space or gap, with control of the magnetic field causing off-switching. H. E. Gallagher and Wolfgang Knauer are inventors of U.S. Pat. No. 3,906,270 and U.S. Pat. No. 3,963,960. Both of these are directed to bipolar structures. Gallagher and Knauer, U.S. Pat. No. 3,906,270 describes a single gap crossed-field switch device wherein the magnetic field is shaped to provide for substantially uniform conduction in either polarity. That patent also identifies the early prior art in crossed magnetic and electric field devices, such as those in the Penning U.S. Pat. No. 2,182,736 and Boucher U.S. Pat. Nos. 3,215,893 and 3,215,939. On the other hand, Gallagher and Knauer, U.S. Pat. No. 3,963,960 is directed to a two interelectrode gap device, one having three electrodes, and it identifies in its background the G. A. G. Hofmann et al, U.S. Pat. No. 3,641,384 which has a three electrode structure with two interelectrode spaces.
In addition, Robin J. Harvey, U.S. Pat. No. 4,123,683 describes another configuration of a crossed-field switch device wherein the concentric electrodes are elongated cylinders to provide an interelectrode space which is elongated in the direction of the cylindrical axis, as compared to the other designs. These background patents are incorporated herein in their entirety by this reference. It is seen that they are all directed to bistable equipment and that several of them are particularly useful because of the sharp cutoff during offswitching.